Some American Lebertia Author(s): Ruth Marshall Source: Transactions of the American Microscopical Society, Vol. 31, No. 4 (Oct., 1912), pp. 225-230 Published by: Wiley on behalf of American Microscopical Society Stable URL: http://www.jstor.org/stable/3221266 . Accessed: 15/05/2014 04:50 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. . Wiley and American Microscopical Society are collaborating with JSTOR to digitize, preserve and extend access to Transactions of the American Microscopical Society. http://www.jstor.org This content downloaded from 194.29.185.222 on Thu, 15 May 2014 04:50:53 AM All use subject to JSTOR Terms and Conditions
Transcript
Some American LebertiaAuthor(s): Ruth MarshallSource: Transactions of the American Microscopical Society, Vol. 31, No. 4 (Oct., 1912), pp.225-230Published by: Wiley on behalf of American Microscopical SocietyStable URL: http://www.jstor.org/stable/3221266 .
Accessed: 15/05/2014 04:50
Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp
.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].
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American Microscopical Society (Published in Quarterly Installments)
Vol. XXXI OCTOBER, 1912 No. 4
SOME AMERICAN LEBERTIA
BY RUTH MARSHALL
The genus Lebertia of the water-mites is easily recognized by the character of the epimera. It belongs to a small group of genera, the subfamily Lebertiinae, characterized by the union of the four pairs of epimera into a single group, with their more or less com- plete fusion. This forms a shield which covers a large part of the ventral surface of the body.
In Lebertia the first and second pairs of plates of the two sides are in contact, while the third is partly fused with the second and fourth. The third and fourth diverge from the median line, and in the bay thus formed lies the genital area. The latter con- sists of two oblong plates, each with three acetabula. The sexes are alike. The covering of the rest of the body is soft or thick- ened, striate, minutely papilliate or developing bits of chitin.
The palpi are small and leg-like; the second joint is stout, the fifth is very small, and all bear bristles or hairs. The legs increase markedly in size from the first to the fourth, and all are tipped with claws. They bear many stout bristles, and sometimes swimming hairs.
Dr. Sig Thor, the Norwegian hydrachnologist, who has made the most extensive studies in the Lebertia, divides the genus into six subgenera; however, the characters which separate the groups seem rather small and inconstant.
Over sixty species have been described; only three of these are from other regions than European, these being from Kamts-
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chatka. L. porosa Thor, a widely distributed European species, has been found in Siberia. L. tauinsignita (Leb.) and L. insignis (Neum.) were reported by Doctor F. Koenike from Canada; but Doctor Thor thinks that these were not identical with the European forms. Three species are described in the present paper, two of which appear to be new. The Lebertia inhabit the colder waters, and this accounts for their very meager occurrence in the author's large collection of water-mites, which came chiefly from the Mis- sissippi basin. One species, however, was found in the Waupaca Chain-o'-Lakes, lakes of glacial origin, in eastern Wisconsin; but the other two came from mountain lakes of the" West. For the latter, the author is indebted to Mr. Chauncey Juday.
Lebertia parmata n. sp.
P1. XXVII, Figs. 4, 5; P1. XXVIII, Figs. 6, 7 This mite resembles L. sparsicapillata Thor closely, but is not
identical with it, as has been determined by a comparison with a specimen of the European form sent to the author by Dr. Thor. The body is oblong, about 1.4 mm. in length. The color cannot be determined, as the material has been in preserving fluids. The group of epimera cover a relatively small part of the ventral sur- face. The cleft between the posterior ends of the second and third plates on each side is longer and wider than is common, and the space between the plates and the genital area is likewise greater. The posterior margin of the fourth epimera is narrow. The gen- ital area is enclosed for only about two-thirds of its length by the approaching margins of the plates. The acetabula are of nearly equal size.
The epimera are covered with pores; the skin of the body at first appears smooth, but small pores and minute parallel striae can be made out by careful focusing. The large glands, of un- known function, described and figured by Thor (1902) for L. porosa were clearly seen close to the fourth epimera, with their long tubes extending to the capitulum (P1. XXVII, Fig. 4).
The palpi have little to distinguish them from typical mem- bers. The last points of the legs are enlarged at the d;stal ends rather noticeably. There are stout bristles on all segments except the sixth, but no swimming hairs are present.
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Four specimens of this species were found in material taken by Mr. Juday from Kern Lake, California, July 20, 1904.
Lebertia artaacetabula n. sp. P1. XXVII, Figs. 1-3
This mite is a small member of the genus, only about 0.8 mm. in length. The nymph measures 0.65 mm. The color cannot be determined. But one adult has been found, together with tree nymphs. They were collected in the Waupaca Lakes, of Wiscon- sin, July Io, 1911. These are the only members of the genus found
by the author in very extensive collections in that state extending over several years.
The epimeral shield covers the greater part of the ventral surface of the body, and extends back a little farther than the genital area. The genital plates are closely fitted into the bay thus formed by the epimera; they are distinctly narrowed at the an- terior end. The chitenous bar at their posterior end is indistinct. The six acetabula are very narrow.
The skin appears to be very finely papilliated; the epimera and the appendages bear fine pores. The last three pairs of legs bear a few swimming hairs. On the joints of all of the middle seg- ments of the legs the broad saber-like bristles are conspicuous, especially at the distal ends.
Lebertia porosa Thor.
P1. XXVIII, Figs. 8-II This species is represented here by one individual only. This
was found in Twin Lakes, Colorado, in the weeds near shore, by Mr. Chauncey Juday, in August, 1902. It measures about 1.6 mm.; the color cannot be determined.
Dr. Thor has kindly sent the author several specimens of L. porosa from Europe. A careful comparison of the American form with these shows but slight differences, such as the little greater width of the fourth epimera, differences which do not appear to justify the formation of a new species, or even a variety, based upon a knowledge of but a single specimen.
The epimera cover a relatively larger area of the body than in L. parmata, and the posterior inner angle of the fourth is conspic- uously broader. The genital plates come up close to the epimera
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and are enclosed by them for about three-fourths of their length. The last pair of acetabula are nearly circular. The skin is finely papilliate, with a few faint irregular lines. The appendages and plates have pores.
The second joint of the palpus is very stout and somewhat bent. The legs are rather slender, and there are not as many stout bristles on the joints as are found in the other two specimens here described. Swimming hairs, however, are found well developed on the fourth and fifth segment of the last two pairs of legs.
PIERSIG, R. 1896. Beitrage zur Kenntnis der in Sachsen einheimischen Hydrachnid-
en-Formen. Inaug. Diss. Leipsig. 1897. Deutschlands Hydrachniden. Bibliotheca Zoologica, XXII:233-
237. Stuttgart, 1897-1900. 1897. Einige neue deutsche Hydrachniden. Zool. Anz., XX:350-35I. I898. Hydrachnidenformen aus der Hohen Tatra. Zool. Anz., XXI:I3. 1901. Hydrachnidae (und Halacaridae). Das Tierreich, XIII:I46-151.
Berlin. SOAR, C. D.
1899. British Freshwater Mites. Science Gossip (n. ser.), VI:44-45. THOR, S.
1897. Bidrag til Kundskaben om Norges Hydrachnider. Arch. Math. Naturv., XIX,6:31.
1898. Andet Bidrag til Kundskaben om Norges Hydrachnider. Arch. Math. Naturv., XX,3,I:40.
1899. Tredie Bidrag til Kundskaben om Norges Hydrachnider. Arch. Math. Naturv., XXI,5:34.
1899. En ny Hydrachnide-slegt og andre nye arter fundne i Norge sommeren 1899. Kristiania.
